The Homeland Security Department and the military this summer will test whether drones flying 65,000 feet above the nation's busiest airports could be used to protect planes from being shot down by terrorists with shoulder-fired missiles.

Dubbed "Project Chloe" after a character on Homeland Security Secretary Michael Chertoff's favorite TV show, 24, the anti-missile strategy is the latest to be explored by government leaders looking to thwart potential missile threats at commercial airports. Other methods are being considered, but Homeland Security officials say they may be too costly or impractical.

The drones, to be tested over the Patuxent River Naval Air Station outside Washington, would be outfitted with missile-warning systems and possibly anti-missile lasers that could send plane-bound missiles veering off course, says Kerry Wilson, a deputy administrator of Homeland Security's anti-missile program.

An unmanned plane's warning indicators could pick up the ultraviolet plume from a missile's rocket booster and trigger an anti-missile laser, which could be shot from the drone or from a site on the ground. That laser would lock on to the missile, essentially blinding it.

The tests follow four years of research on anti-missile laser systems that could be mounted on the bellies of planes for $1 million or more per plane.

Those systems, regularly used by the military, are being tested on nine Federal Express cargo planes to see how well they hold up. Early military tests showed they broke down after 300-400 hours of use, a failure rate that's problematic for commercial use.

Concerns about those systems prompted officials to look for a less expensive, more reliable solution, and using unmanned aerial vehicles "is an idea worth looking at," Wilson said.

Project Chloe has critics in Congress and in private industry.

Rep. Steve Israel, D-N.Y., says the government should share the cost of installation and maintenance of the more expensive systems with the airline industry. "It's been four years of trying to figure out how to get this cheaper," he says. "But it's just a matter of time before a shoulder-fired missile becomes the biggest blow to our economy."

Aviation groups have expressed concerns about drones in civilian airspace. Chris Dancy of the Aircraft Owners and Pilots Association says there would be no problem with drones flying at 65,000 feet, well above the altitude of commercial jets. He said he was concerned, however, about how airspace would be restricted when the drones take off and land.

Inexpensive, widely available shoulder-fired missiles have been used against passenger and cargo planes overseas. Although no one has tried to take down a plane in the USA, Homeland Security is concerned about the possibility.

A Rq-4A Global Hawk begins its descent with an initial decrease in altitude to 20,000 feet. The RQ-4A Global Hawk is one of the largest of a breed of pilotless airships that may help revolutionize the war on terrorism.